U.S. patent application number 10/936966 was filed with the patent office on 2005-03-10 for optical sheet and process for producing the same.
Invention is credited to Amemiya, Hiroyuki, Ohtaki, Hiroyuki, Yamagata, Hideaki.
Application Number | 20050052737 10/936966 |
Document ID | / |
Family ID | 34228035 |
Filed Date | 2005-03-10 |
United States Patent
Application |
20050052737 |
Kind Code |
A1 |
Amemiya, Hiroyuki ; et
al. |
March 10, 2005 |
Optical sheet and process for producing the same
Abstract
Disclosed are a fine-pitch and lightweight optical sheet and a
production process which can produce the optical sheet very easily
at low cost. The optical sheet comprises an optical function layer
formed of a thermoplastic resin. The optical function layer has
been formed by shaping the surface of the thermoplastic resin into
cylindrical lenses, and the pitch of the shaped cylindrical lenses
is not more than 150 .mu.m.
Inventors: |
Amemiya, Hiroyuki;
(Tokyo-to, JP) ; Yamagata, Hideaki; (Tokyo-to,
JP) ; Ohtaki, Hiroyuki; (Tokyo-to, JP) |
Correspondence
Address: |
HARNESS, DICKEY & PIERCE, P.L.C.
P.O. BOX 828
BLOOMFIELD HILLS
MI
48303
US
|
Family ID: |
34228035 |
Appl. No.: |
10/936966 |
Filed: |
September 9, 2004 |
Current U.S.
Class: |
359/456 |
Current CPC
Class: |
G03B 21/62 20130101 |
Class at
Publication: |
359/456 |
International
Class: |
G03B 021/60 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 9, 2003 |
JP |
2003-316841 |
Sep 24, 2003 |
JP |
2003-332349 |
Claims
1. An optical sheet comprising an optical function layer formed of
a thermoplastic resin, said optical function layer having been
formed by shaping the surface of the thermoplastic resin into
cylindrical lenses, the pitch of the shaped cylindrical lenses
being not more than 150 .mu.m.
2. The optical sheet according to claim 1, which further comprises
a substrate film layer.
3. The optical sheet according to claim 1, wherein said optical
function layer has a thickness of not more than 200 .mu.m,
preferably not more than 150 .mu.m.
4. The optical sheet according to claim 1, wherein said
thermoplastic resin has a softening temperature of 80 to
180.degree. C.
5. The optical sheet according to any one of claims 1 to 4, which
further comprises, on the side which is opposite to the cylindrical
lenses, a striped light shielding layer directly or through a
pressure-sensitive adhesive layer.
6. The optical sheet according to claim 5, wherein a support is
provided on the striped light shielding layer directly or through
an adhesive layer.
7. The optical sheet according to claim 6, wherein said support has
a saturated water absorption elongation of not more than 0.3%.
8. Use of the optical sheet according to claim 1 in a transmission
screen light diffusing sheet.
9. A process for producing the optical sheet according to claim 2,
said process comprising the steps of: a) extruding and delivering a
molten thermoplastic resin continuously onto a substrate film being
moved; b) pressing a molding roll against the thermoplastic resin
provided on the substrate film to transfer a shaping pattern on the
surface of the molding roll onto the thermoplastic resin and thus
to shape the surface of the thermoplastic resin into cylindrical
lenses, and continuously delivering a laminate structure of the
shaped thermoplastic resin and the substrate film; and c)
subsequently curing the shaped thermoplastic resin and then
separating the substrate film from the assembly to produce said
optical sheet or providing said optical sheet without the
separation of the substrate film.
10. A lenticular lens sheet for a transmission screen, said
lenticular lens sheet comprising (A) a transparent or
semitransparent sheet formed of a thermoplastic resin, (B) a
photosensitive pressure-sensitive adhesive layer, (C) a light
shielding part, (D) an adhesive layer, and (E) a transparent or
semitransparent support formed of a thermoplastic resin which have
been successively formed in that order, said sheet (A) having
cylindrical lenses with a pitch of not more than 150 .mu.m on one
side of the sheet, and having a sheet thickness of not more than
200 .mu.m, said light shielding part (C) being in the form of a
stripe having a width of not more than 130 .mu.m.
11. The lenticular lens sheet for a transmission screen according
to claim 10, wherein said photosensitive pressure-sensitive
adhesive layer (B) is formed of a photosensitive adhesive that,
upon a radical reaction, undergoes a lowering in adhesive strength
at its exposed part.
12. The lenticular lens sheet for a transmission screen according
to claim 11, wherein the adhesive strength of said photosensitive
pressure-sensitive adhesive in its exposed part is lower by not
less than 50% than the unexposed part.
13. The lenticular lens sheet for a transmission screen according
to claim 10, wherein said sheet (A) comprises a substrate film
layer and a cylindrical lens layer.
14. The lenticular lens sheet for a transmission screen according
to claim 10, wherein said photosensitive pressure-sensitive
adhesive layer (B) comprises a photosensitive pressure-sensitive
adhesive resin composition comprising at least an acrylic ester
pressure-sensitive adhesive resin, a photoradically polymerizable
compound, or a photoradical polymerization initiator system.
15. The lenticular lens sheet for a transmission screen according
to claim 10, wherein said light shielding part (C) contains a light
shielding pigment and the content of the light shielding pigment in
the light shielding part is at least 1.5 times larger than other
solid contents contained in the light shielding part.
16. A process for producing the lenticular lens sheet for a
transmission screen according to claim 10, said process comprising
the steps of: a) transferring a shaping pattern onto a molten
extruded thermoplastic resin to prepare a not more than 200
.mu.m-thick transparent or semitransparent sheet (A) with
cylindrical lenses being shaped therein at a pitch of not more than
150 .mu.m; b) forming a photosensitive pressure-sensitive adhesive
layer (B) on the transparent or semitransparent sheet (A), formed
in step (a), on the flat side which is opposite to the cylindrical
lenses; c) applying light at a collimation angle of not more than
10 degrees to the sheet, prepared in step (b), on its side where
the cylindrical lenses are formed, whereby the adhesive strength of
the photosensitive pressure-sensitive adhesive in its part exposed
to light focused by the cylindrical lenses is lowered by a radical
reaction; d) laminating a light shielding layer transfer sheet
comprising a material for light shielding part formation onto the
photosensitive pressure-sensitive adhesive layer in the sheet
prepared in step (c); e) separating the light shielding layer
transfer sheet laminated in step (d) to transfer the material for
light shielding part formation onto the unexposed part in the
photosensitive pressure-sensitive adhesive layer (B), thereby
forming a striped light shielding part; and f) forming an adhesive
layer (D) and a transparent or semitransparent support (E) formed
of a thermoplastic resin on the sheet prepared in step (e).
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to an optical sheet and a
process for producing the optical sheet. More particularly, the
present invention relates to a cylindrical lens-shaped optical
sheet and a lenticular lens sheet for a transmission screen.
[0003] 2. Background Art
[0004] Various optical sheets have hitherto been proposed. For
example, in transmission screen sheets, particularly diffusive
sheets for transmission screens for projection televisions, shaping
of the surface thereof into lenses has been carried out.
[0005] In such diffusive sheets for transmission screens, in
general, at least one side of a sheet formed of a transparent or
semitransparent material is formed into a lenticular shape while a
striped light shielding layer is provided on the other side of the
sheet.
[0006] Regarding techniques in connection with such optical sheets,
for example, Japanese Patent Laid-Open No. 338606/2000, Japanese
Patent Laid-Open No. 209131/2001, Japanese Patent Laid-Open No.
174859/2002, and Japanese Patent Laid-Open No. 303709/2002 disclose
that a resin composition formed into a lenticular shape is
polymerized and cured by applying an ionizing radiation such as a
radiation, ultraviolet light, or electron beams. This method
utilizing an ionizing radiation for polymerization and curing of
the resin is advantageous in that the shape of the mold can be very
faithfully reproduced on the surface of the molded product.
[0007] Since, however, radiation curing resins and photosensitive
resins are relatively expensive, the production cost of optical
lens sheets is increased. Further, when there is damage to the
mold, disadvantageously, the damage is also of course faithfully
reproduced on the surface of the molded product. In general, the
damage to the mold often occurs in an acute-angle tip part of the
mold (that is, for example, in the mold for lenticular lens, the
damage occurs in the concave part of the lenticular lens). For this
reason, a production technique utilizing extrusion using a
thermoplastic resin instead of the ionizing radiation curing resin
has been desired. Specifically, the development of a technique
utilizing a thermoplastic resin is desired in which the damage to
the mold is less likely to be reflected in the final molded
product, whereby a deterioration in optical properties can be
prevented.
[0008] In recent years, an increase in quality of image
representation and an increase in size of screens have led to a
demand for optical sheets which can produce high-definition images
and can be produced easily at low cost. In diffusive sheets for
transmission screens, narrowing the pitch of the lens element, that
is, the adoption of fine pitch, is a method effective for producing
high-definition images. The pitch of a light shielding layer
provided on the other side of the sheet corresponds to the pitch of
the lenses. Therefore, the pitch of the light shielding layer
should be narrowed with decreasing the pitch of the lenticular
lenses.
[0009] When lenses are molded by a conventional extrusion method
using a thermoplastic resin, however, finer pitch than a given
level cannot be realized without difficulties due to limitation
derived from processing accuracy of the lenticular lens side.
Specifically, lenses can be relatively stably provided at a pitch
of about 500 .mu.m, whereas lenses at a finer pitch (for example,
not more than 200 .mu.m) than about 500 .mu.m cannot be provided
without difficulties.
[0010] Further, when lenses are shaped by applying high pressure
for the formation of a thinner sheet, in some cases, an optical
function layer having a lens shape is disadvantageously broken.
[0011] Conventional methods proposed for forming a striped light
shielding part include the so-called "wet process" which comprises
coating a light shielding toner or a black ink onto a
photosensitive pressure-sensitive adhesive layer, exposing the
coating, washing nonexposed areas with water to remove the light
shielding toner and the like from the nonexposed area, and a dry
process utilizing a cationic polymerization reaction in a
photosensitive pressure-sensitive adhesive.
[0012] The photosensitive pressure-sensitive adhesive utilizing the
cationic polymerization reaction, however, suffers from high
material cost, and short pot life which makes it difficult to
handle during processing.
SUMMARY OF THE INVENTION
[0013] Accordingly, an object of the present invention is to
provide an optical sheet, which has a fine pitch and is lightweight
as a light diffusive sheet or a lenticular lens sheet for a
transmission screen, and a production process which can produce the
optical sheet very easily at low cost.
[0014] According to a first aspect of the present invention, there
is provided an optical sheet comprising an optical function layer
formed of a thermoplastic resin, said optical function layer having
been formed by shaping the surface of the thermoplastic resin into
cylindrical lenses, the pitch of the shaped cylindrical lenses
being not more than 150 .mu.m.
[0015] According to a second aspect of the present invention, there
is provided a process for producing the above optical sheet, said
process comprising the steps of:
[0016] a) extruding and delivering a molten thermoplastic resin
continuously onto a substrate film being moved;
[0017] b) pressing a molding roll against the thermoplastic resin
provided on the substrate film to transfer a shaping pattern on the
surface of the molding roll onto the thermoplastic resin and thus
to shape the surface of the thermoplastic resin into cylindrical
lenses, and continuously delivering a laminate structure of the
shaped thermoplastic resin and the substrate film; and
[0018] c) subsequently curing the shaped thermoplastic resin and
then optionally separating the substrate film from the
assembly.
[0019] According to a third aspect of the present invention, there
is provided a lenticular lens sheet for a transmission screen, said
lenticular lens sheet comprising (A) a transparent or a
semitransparent sheet formed of a thermoplastic resin, (B) a
photosensitive pressure-sensitive adhesive layer, (C) a light
shielding part, (D) an adhesive layer, and (E) a transparent or
semitransparent support formed of a thermoplastic resin which have
been successively formed in that order,
[0020] said sheet (A) having cylindrical lenses with a pitch of not
more than 150 .mu.m on one side of the sheet, and having a sheet
thickness of not more than 200 .mu.m,
[0021] said light shielding part (C) being in the form of a stripe
having a width of not more than 130 .mu.m.
[0022] According to a fourth aspect of the present invention, there
is provided a process for producing a lenticular lens sheet for a
transmission screen, said process comprising the steps of:
[0023] a) transferring a shaping pattern onto a molten extruded
thermoplastic resin to prepare a not more than 200 .mu.m-thick
transparent or semitransparent sheet (A) with cylindrical lenses
being shaped therein at a pitch of not more than 150 .mu.m;
[0024] b) forming a photosensitive pressure-sensitive adhesive
layer (B) on the transparent or semitransparent sheet (A), formed
in step (a), on the flat side which is opposite to the cylindrical
lenses;
[0025] c) applying light at a collimation angle of not more than 10
degrees to the sheet, prepared in step (b), on its side where the
cylindrical lenses are formed, whereby the adhesive strength of the
photosensitive pressure-sensitive adhesive in its part exposed to
light focused by the cylindrical lenses is lowered by a radical
reaction;
[0026] d) laminating a light shielding layer transfer sheet
comprising a material for light shielding part formation onto the
photosensitive pressure-sensitive adhesive layer in the sheet
prepared in step (c);
[0027] e) separating the light shielding layer transfer sheet
laminated in step (d) to transfer the material for light shielding
part formation onto the unexposed part in the photosensitive
pressure-sensitive adhesive layer (B), thereby forming a striped
light shielding part; and
[0028] f) forming an adhesive layer (D) and a transparent or
semitransparent support (E) formed of a thermoplastic resin on the
sheet prepared in step (e).
[0029] In the present invention, since neither a radiation curing
resin nor a photosensitive resin is used in the lens part, an
optical sheet (a lenticular lens sheet for a light transmission
screen) can be produced at low cost.
[0030] Further, since the optical function layer (a layer provided
with cylindrical lenses) is formed of a thermoplastic resin, the
damage to the mold is less likely to be reflected in the final
molded product and, as a result, a deterioration in optical
properties can be prevented.
[0031] Furthermore, in the present invention, the so-called
"extrusion emboss lamination molding is used in which the supply
and transfer of the substrate film, extrusion in which the supply
of a thermoplastic resin and surface shaping are carried out, and a
lamination step are carried out continuously. Therefore, the
thickness of the optical function layer of the optical sheet can be
rendered thin.
[0032] Further, a fine-pitch and light-weight optical sheet can be
produced as a light diffusive sheet or lenticular lens sheet for a
transmission screen very easily at low cost.
[0033] In the lenticular lens sheet for an optical transmission
screen according to the present invention, a lenticular lens sheet
for an optical transmission screen provided with cylindrical lenses
at a fine pitch of not more than 150 .mu.m can be realized by
forming the cylindrical lens layer using a thermoplastic resin and
rendering the thickness of the cylindrical lens layer small.
BRIEF DESCRIPTION OF THE DRAWINGS
[0034] FIG. A1 is a typical cross-sectional view of an optical
sheet which is a preferred embodiment of the present invention;
[0035] FIG. A2 is a typical cross-sectional view of an optical
sheet which is a preferred embodiment of the present invention;
[0036] FIG. A3 is a typical cross-sectional view of an optical
sheet which is a preferred embodiment of the present invention;
[0037] FIG. A4 is a typical cross-sectional view of an optical
sheet which is a preferred embodiment of the present invention;
[0038] FIG. A5 is a perspective view of the optical sheet shown in
FIG. A1;
[0039] FIG. A6 is a perspective view of the optical sheet shown in
FIG. A4;
[0040] FIG. A7 is a schematic diagram illustrating a production
process of an optical sheet according to the present invention;
[0041] FIG. A8 is a schematic diagram illustrating another
embodiment of the production process of an optical sheet according
to the present invention;
[0042] FIG. B1 is a typical cross-sectional view of a lenticular
lens sheet for a transmission screen in a preferred embodiment of
the present invention;
[0043] FIG. B2 is a schematic diagram of an embodiment of an
apparatus used in the production process of a lenticular lens sheet
for a transmission screen according to the present invention;
[0044] FIG. B3 is a schematic cross-sectional view showing an
embodiment of a sheet prepared in step (b) according to the present
invention;
[0045] FIG. B4 is a schematic cross-sectional view showing an
embodiment of a sheet prepared in step (e) according to the present
invention; and
[0046] FIG. B5 is a schematic diagram of another embodiment of an
apparatus used in the production process of a lenticular lens sheet
for a transmission screen according to the present invention.
DETAILED DESCRIPTION OF THE INVENTION
[0047] The present invention will be described, if necessary, with
reference to the accompanying drawings.
[0048] 1. Optical Sheet According to First Aspect of the
Invention
[0049] FIGS. A1 to A4 are schematic cross-sectional views of
preferred embodiments of the optical sheet according to the present
invention. FIG. A5 is a perspective view of the optical sheet
according to the present invention shown in FIG. A1.
[0050] An optical sheet (1) according to the present invention
shown in FIG. A1 is an optical sheet comprising a substrate film
layer (2) and an optical function layer (3) formed of a
thermoplastic resin. The optical function layer (3) is a layer
formed by shaping the surface of the thermoplastic resin into
cylindrical lenses, and the pitch of the shaped cylindrical lenses
is not more than 150 .mu.m. The optical sheet according to the
present invention may not be provided with the substrate film layer
(2).
[0051] The optical sheet (1) shown in FIG. A1 is particularly
suitable for an optical sheet for constituting a light diffusive
sheet in a transmission screen for projection televisions.
[0052] Details (for example, constituents, surface state or form of
the shaped surface and thickness) of the cylindrical lenses as the
optical function layer (3) can be properly determined according to
the applications of the optical sheet (1) of the present invention.
The thickness of the optical function layer (3) (that is, distance
between the flat face on the substrate film layer (2) side and the
apex of the convex in the lens) is not more than 150 .mu.m,
particularly not more than 100 .mu.m. The shaped surface may not be
necessarily such that regular patterns are continuously
arranged.
[0053] The substrate film layer (2) may be formed of various
thermoplastic resins and thermosetting resins so far as they have
properties required of the substrate for an optical sheet, for
example, transparency, strength, durability and the like. Preferred
thermoplastic resins include polyethylene terephthalate (PET),
polystyrene (PS), polycarbonate (PC), polymethyl methacrylate
(PMMA), polyvinyl chloride (PVC), polyethylene (PE),
tetrafluoroethylene (PTFE), and copolymer resins containing at
least one of these resins.
[0054] The thickness of the substrate film layer (2) may be
properly determined depending upon specific applications of the
optical sheet and the strength and the like required of the optical
sheet. In the present invention, the thickness of the substrate
film layer may be 25 to 150 .mu.m, preferably 50 to 100 .mu.m.
[0055] The optical function layer (3) is formed by extruding a
molten thermoplastic resin onto the substrate film layer (2) and
has a shaped surface. The thermoplastic resin constituting the
optical function layer (3) has good transparency, strength, and
durability, and, at the same time, can be extruded and shaped with
good stability and operability, and can provide a predetermined
optical function.
[0056] Such thermoplastic resins include polystyrene (PS),
polycarbonate (PC), polymethyl methacrylate (PMMA), polyvinyl
chloride (PVC), polyethylene (PE), tetrafluoroethylene (PTFE),
polypropylene (PP), and copolymer resins containing at least one of
these resins.
[0057] Among the above thermoplastic resins, resins having a
softening temperature of 80 to 180.degree. C., particularly 90 to
150.degree. C., are preferred. The term "softening temperature" as
used herein refers to a Vicat softening temperature as measured by
the method specified in JIS K 7206.
[0058] Preferably, the thermoplastic resin has a coefficient of
linear expansion of not more than 9.times.10.sup.-5/.degree. C.
Here the coefficient of linear expansion refers to a value as
measured by the method specified in JIS K 7197.
[0059] Further, preferably, the thermoplastic resin has a water
absorption of not more than 0.3%, particularly preferably not more
than 0.2%. Here the water absorption refers to a value as measured
by the method specified in JIS K 7209.
[0060] Among the thermoplastic resins in the above preferred
embodiments, the thermoplastic resin having a coefficient of linear
expansion of not more than 9.times.10.sup.-5/.degree.C. is more
preferred.
[0061] As compared with the conventional radiation curing resins
and photosensitive resins, the thermoplastic resin used in the
present invention are much more inexpensive and does not always
require the use of a photopolymerization initiator or the like.
Therefore, neither coloration of the resin attributable to the
photopolymerization initiator or the like nor a lowering in
transparency occurs. This enables an optical sheet having excellent
transparency, color tone reproduction, and stability to be produced
at low cost.
[0062] When the above thermoplastic resin is used, a slight thermal
resilience phenomenon is sometimes observed in the shaped surface
of the thermoplastic resin layer. In the present invention, even
when some damage to the surface of a molding roll used in shaping
is present, the use of the thermoplastic resin permits the
reproduced damage to the shaped surface of the optical function
layer (3) to be repaired by the thermal resilience and thus to be
rendered visually unnoticeable. Thus, an improvement in optical
properties can be realized. When the optical function layer is
provided at a fine pitch for high-quality image representation, the
above effect is significant.
[0063] In the production process of an optical sheet according to
the present invention, a method may be adopted in which the
thermoplastic resin is previously palletized and the pellets are
melted and used in the production of the optical sheet. For
example, when additives (for example, light diffusing agents and
colorants) are mixed in a thermoplastic resin or when two or more
thermoplastic resins are used, the resin composition can be
suitably regulated by mixing previously prepared pellets together
and melting the mixture, or by mixing pellets in a molten resin and
melting the mixture. The regulation can be suitably carried out
even when the difference in specific gravity between the mixing
ingredients is large or even when the viscosity of the resin is
relatively high.
[0064] FIGS. A2 to A4 are schematic cross-sectional views of
optical sheets in other preferred embodiments of the present
invention. FIG. A6 is a perspective view of the optical sheet
according to the present invention shown in FIG. A4.
[0065] In an optical sheet (1) according to the present invention
shown in FIG. A2, an adhesive layer (4) is interposed between the
substrate film layer (2) and the optical function layer (3).
[0066] In an optical sheet (1) according to the present invention
shown in FIG. A3, a striped light shielding layer (6) is provided
through a pressure-sensitive adhesive layer (5) on the substrate
film layer (2) which is opposite to the optical function layer (3).
A construction may also be adopted in which the pressure-sensitive
adhesive layer (5) is omitted and the striped light shielding layer
(6) is provided directly on the substrate film layer (2). Further,
a construction may also be adopted in which the substrate film
layer (2) is omitted and the pressure-sensitive adhesive layer (5)
or the striped light shielding layer (6) is directly provided.
[0067] In an optical sheet (1) according to the present invention
shown in FIG. A4, a support (8) is provided through an adhesive
layer (7) on the striped light shielding layer (6). A construction
may also be adopted in which the adhesive layer (7) is omitted and
the support (8) is provided directly on the light shielding layer
(6). Regarding the pressure-sensitive adhesive layer (5) in its
parts on which the striped light shielding layer (6) is not
provided, the adhesive layer (7) is provided directly on the
pressure-sensitive adhesive layer (5) (when the adhesive layer (7)
is omitted, the support (8) is provided directly on the
pressure-sensitive adhesive layer (5)).
[0068] In the optical sheet (1) shown in FIG. A2 or FIG. A4, the
adhesive layer (4, 7) may be formed of any material so far as
satisfactory adhesive strength is provided between the adhesive
layer (4, 7) and layers in contact with the adhesive layer (4, 7)
(for example, the substrate film layer (2), the optical function
layer (3), the pressure-sensitive adhesive layer (5), the light
shielding layer (6), and the support (8)) and, in addition, the
material has substantially no adverse effect on each layer and the
function, properties and the like of the optical sheet per se.
[0069] The thickness of the adhesive layer (4, 7) may be determined
by taking into consideration, for example, the material of each
layer constituting the optical sheet and the necessary adhesive
strength. The adhesive layer (4) which functions to adhere the
optical function layer (3) to the substrate film layer (2) may be
formed of an isocyanate, vinyl acetate or the like, and the
adhesive layer (7) which functions to adhere the light shielding
layer (6) to the support (8) may be formed of a urethane resin,
acrylic resin, epoxy resin or the like.
[0070] When the optical function layer (3) is in the form of
lenticular lenses as shown in FIG. A3, the light shielding layer
(6) is formed in a region through which light focused by the lenses
is not to be passed. In the optical sheet (1) shown in FIGS. A1 to
A4, light is incident from the lower side of the optical sheet (1),
is focused by the optical function layer 3, and is then passed,
toward above the optical sheet (1), through a region where the
light shielding layer (6) is not provided. The region impermeable
to light focused by the optical function layer (3) is provided in a
stripe form corresponding to the shaped surface of the optical
function layer (3). Therefore, the light shielding layer (6) also
becomes a stripe form. Preferably, the light shielding layer (6)
may be formed of a black light shielding material, for example,
carbon black, black ink, or black toner.
[0071] The ratio of the striped light shielding layer (6) to the
lens pitch (b in FIG. A3) is preferably 50 to 90%. According to the
present invention, since an optical sheet with the light shielding
layer (6) provided at this high ratio is provided, a high-quality
image can be realized.
[0072] The light shielding layer (6) can be formed by various
methods. In the present invention, the light shielding layer (6)
may be formed by forming a pressure-sensitive adhesive layer (a
pressure-sensitive adhesive layer 5) which causes disappearance or
a lowering of tackiness upon-exposure to light (mainly ultraviolet
irradiation) on the substrate film (2), allowing light (mainly
ultraviolet light) focused by the optical function layer (3) to act
on the pressure-sensitive layer (5) to cause disappearance or a
lowering of tackiness of the pressure-sensitive adhesive layer (5)
in its region through which light is to be passed, and then coating
a light shielding layer forming material (for example,
finely-powdered carbon black or black ink) to adhere the light
shielding layer forming material onto only the pressure-sensitive
adhesive layer (5) in its tacky region (that is, light impermeable
parts).
[0073] The pressure-sensitive adhesive layer (5) may be formed of,
for example, a material prepared by mixing a radical reaction
initiator into a radically reactive resin material.
[0074] In the optical sheet (1) according to the present invention,
as shown in FIG. A4, if necessary, the support (8) may be provided.
The support (8) may be any one. Preferably, however, the support
(8) has a saturated water absorption elongation of not more than
0.3%, particularly preferably not more than 0.2%. Resins satisfying
this requirement include methyl methacrylate-styrene copolymer (MS
resin).
[0075] Further, in the optical sheet according to the present
invention, a light diffusing function can be imparted to at least
one layer constituting the optical sheet (1). The light diffusing
function can be imparted by adding a light diffusing agent (for
example, acrylic beads, styrene beads, or glass beads) to any of
the layers.
[0076] In the optical sheet according to the present invention, at
least one layer (preferably, any one or at least two layers of the
substrate sheet layer (2), the optical function layer (3), the
support (8), and other layers (not shown)) constituting the optical
sheet (1) may have a nonglare, antistatic, or
contamination-resistant property.
[0077] In the optical sheet (1) according to the present invention
shown in FIGS. A1 to A4, for example, a nonglare layer, an
antistatic layer, and/or a contamination-resistant layer (not
shown) may be additionally provided according to need.
[0078] 2. Production Process of Optical Sheet According to Second
Aspect of Invention
[0079] FIG. A7 is a schematic diagram of a preferred embodiment of
the production process of an optical sheet according to the present
invention.
[0080] The production process of an optical sheet according to the
present invention shown in FIG. A7 comprises the steps of:
[0081] a) extruding and delivering a molten thermoplastic resin
continuously onto a substrate film being moved;
[0082] b) pressing a molding roll against the thermoplastic resin
provided on the substrate film to transfer a shaping pattern on the
surface of the molding roll onto the thermoplastic resin and thus
to shape the surface of the thermoplastic resin into cylindrical
lenses, and continuously delivering a laminate structure of the
shaped thermoplastic resin and the substrate film; and
[0083] c) subsequently curing the shaped thermoplastic resin and
then separating the substrate film from the assembly to produce
said optical sheet or providing said optical sheet without the
separation of the substrate film.
[0084] Carrying out steps a) to c) consecutively in that order in a
part of the whole process suffices for the production process of an
optical sheet according to the present invention. Therefore, for
example, other step(s) or procedure(s) may be carried out before
carrying out step a) or after carrying out step c), or, if
necessary, between consecutive two steps of steps a) to c).
[0085] Each step will be described.
[0086] (1) Step (a)
[0087] In the production process of an optical sheet according to
the present invention shown in FIG. A7, a substrate film (10) is
supplied from a substrate film supply source (14) and is moved
leftward from the substrate film supply source (14). The substrate
film (10) comes into contact with a pressing roll (18), is moved on
the roll surface part in the pressing roll (18) in accordance with
the rotation of the pressing roll (18), is then passed through a
press contact point (19) between the pressing roll (18) and a
molding roll (12), and is moved according to the rotation of the
molding roll (12) in such a state that the thermoplastic resin
layer and the substrate film are stacked on top of each other.
[0088] When the optical sheet having the adhesive layer (4) as
shown in FIG. 2A is produced, a laminate comprising an adhesive
layer provided on a substrate film may be provided in the substrate
film supply source (14).
[0089] The thermoplastic resin constituting the optical function
layer (3) in the optical sheet according to the present invention
is supplied, for example, as pellets from a hopper (15) into a
barrel (16) where the resin is heated to a predetermined
temperature. The resin is then continuously supplied in a molten
state through a die (17) onto a substrate film (10) being
moved.
[0090] The thermoplastic resin may be continuously supplied so as
to come into contact simultaneously with the substrate film and the
molding roll. The amount of the molten thermoplastic resin supplied
may be properly determined by taking into consideration, for
example, the quantity of movement of the substrate film (10), the
thickness of the optical function layer, and the shape of molded
cylindrical lenses.
[0091] (2) Step (b)
[0092] In the production process of an optical sheet according to
the present invention shown in FIG. A7, a molding roll (12) is
pressed against the thermoplastic resin (11) on the substrate film
(10) to transfer the shaped pattern (12a) of the surface of the
molding roll (12) to the thermoplastic resin (11), whereby the
thermoplastic resin (11) is shaped into lenses. The shaped pattern
(12a) may be determined so that a predetermined shaped surface is
formed in the optical function layer.
[0093] The molding roll (12) continuously delivers a laminate (13)
of the molded thermoplastic resin (11) and the substrate film (10).
The substrate film (10) and the thermoplastic resin (11) are
simultaneously supplied into between the molding roll (12) and the
pressing roll (18) provided opposite to the molding roll (12) and,
at the same time, are molded and extruded in a continuous manner.
The shaped pattern (12a) in this molding roll (12) may be provided
so that the direction of movement of the substrate film (10) (a
direction indicated by an arrow in FIG. 7) is parallel to the
direction of lens convex part (or the lens concave part) of
cylindrical lenses. Alternatively, a construction may be adopted in
which the direction of movement of the substrate film (10) is
orthogonal to the direction of the lens convex part (or the lens
concave part) of the cylindrical lenses. In the present invention,
preferably, the direction of movement of the substrate film (10) is
parallel to the direction of the lens convex part (or the lens
concave part) of the cylindrical lenses.
[0094] The radius of the molding roll (12) is not necessarily
identical to and may be different from the radius of the pressing
roll (18). The molding roll (12) and the pressing roll (18) each
may be provided with temperature control means, and the temperature
of both the rolls may also be regulated to respective optical
ranges so that a good optical sheet can be provided.
[0095] (3) Step (c)
[0096] In step (c), the thermoplastic resin (11) shaped into lenses
is cured. After curing the thermoplastic resin, the substrate sheet
may be separated to prepare an optical sheet consisting of the
thermoplastic resin layer alone. After step (c), other layer(s)
(for example, a light shielding layer) may be formed.
[0097] 3. Production Process of Optical Sheet According to Other
Aspect of Invention
[0098] FIG. A8 is a schematic diagram of the production process of
an optical sheet according to other aspect of the present
invention.
[0099] The production process of an optical sheet according to the
present invention shown in FIG. A8 comprises the steps of:
[0100] a) extruding and delivering a molten thermoplastic resin
continuously onto a substrate film being moved;
[0101] b) pressing a molding roll against the thermoplastic resin
provided on the substrate film to transfer a shaping pattern on the
surface of the molding roll onto the thermoplastic resin and thus
to shape the surface of the thermoplastic resin into cylindrical
lenses, and continuously delivering a laminate structure of the
shaped thermoplastic resin and the substrate film; and
[0102] c) subsequently curing the shaped thermoplastic resin and
then separating the substrate film from the assembly to produce
said optical sheet or providing said optical sheet without the
separation of the substrate film,
[0103] the molten thermoplastic resin in step a) being supplied to
a position on the upstream side of the direction of supply of the
substrate film as compared with the pressing position of the
molding roll in step b).
[0104] As shown in FIG. A8, preferably, the molten thermoplastic
resin is supplied to a position (20) on the substrate film (10)
being moved and on the upstream side of the direction of supply of
the substrate film (10) (that is, substrate film supply source (14)
side) as compared with the molding roll (12) pressing position. In
general, a reservoir part called "bulk" of the molten thermoplastic
resin occurs around the press contact point (19) part between the
pressing roll (18) and a molding roll (12) in accordance with the
relationship between the extrusion output of the thermoplastic
resin supplied from the die (17) onto the substrate film (10) and
the amount of the thermoplastic resin shaped into the cylindrical
lenses by the molding roll (12). In the present invention, the
molten thermoplastic resin is supplied to the position (20) on the
upstream side of the direction of supply of the substrate film (10)
compared with the position of the bulk.
[0105] It is estimated that, in this bulk part, a local change in
viscosity, properties, and flow direction of the thermoplastic
resin occurs, for example, due to the weight of the molten
thermoplastic resin per se, the movement of the substrate film
(10), suction caused by the rotation of the pressing roll (18) and
the molding roll (12), and a pressure change and a temperature
change caused by shaping. In the present invention, the reason why
the thickness of the optical function layer can be reduced and
cylindrical lenses having a fine pitch of not more than 150 .mu.m
can be realized is considered to reside in that the properties and
state of the thermoplastic resin during molding can be optimized
for cylindrical lens molding by supplying the molten thermoplastic
resin to a specific position.
[0106] In the present invention, the so-called "extrusion emboss
lamination molding," in which the supply and transfer of the
substrate film, extrusion of a thermoplastic resin, and a
lamination step are carried out continuously, is used. Therefore,
the thickness of the optical function layer of the optical sheet
can be rendered thin, and an optical sheet with cylindrical lenses
having a pitch of not more than 150 .mu.m unattainable by the prior
art technique can be provided.
[0107] Further, the optical sheet can be produced using an
inexpensive thermoplastic resin in a continuous and stable manner.
Therefore, the production efficiency is high, and the cost
effectiveness is good.
[0108] 4. Lenticular Lens Sheet for Transmission Screen According
to Third Aspect of Invention
[0109] FIG. B1 is a typical cross-sectional view of a lenticular
lens sheet for a transmission screen in a preferred embodiment of
the present invention.
[0110] A lenticular lens sheet (21) for a transmission screen
according to the present invention shown in FIG. B1 is a lenticular
lens sheet for a transmission screen, said lenticular lens sheet
comprising (A) a transparent or a semitransparent sheet formed of a
thermoplastic resin, (B) a photosensitive pressure-sensitive
adhesive layer, (C) a light shielding part, (D) an adhesive layer,
and (E) a transparent or semitransparent support formed of a
thermoplastic resin which have been successively formed in that
order,
[0111] said sheet (A) having cylindrical lenses with a pitch of not
more than 150 .mu.m on one side of the sheet and having a thickness
of not more than 200 .mu.m,
[0112] said light shielding part (C) being in the form of a stripe
having a width of not more than 130 .mu.m.
[0113] The lenticular lens sheet (21) for a transmission screen
shown in FIG. B1 is particularly suitable as a lenticular lens
sheet in a transmission screen for projection televisions.
[0114] The construction of the lenticular lens sheet for a
transmission screen will be described.
[0115] (1) Transparent or Semitransparent Sheet
[0116] In the transparent or semitransparent sheet (A), the pitch
of the cylindrical lenses is preferably not more than 150 .mu.m,
particularly preferably 50 to 100 .mu.m. The thickness of the
transparent or semitransparent sheet (A) is preferably not more
than 200 .mu.m, particularly preferably 50 to 150 .mu.m.
[0117] FIG. B1 shows a transparent or semitransparent sheet (A)
composed of a cylindrical lens layer (A1) and a substrate film
layer (A2). This transparent or semitransparent sheet (A) composed
of the cylindrical lens layer (A1) and the substrate film layer
(A2) is a preferred embodiment of the present invention. In the
present invention, however, the transparent or semitransparent
sheet (A) may consist of the cylindrical lens layer (A1) alone.
[0118] (2) Cylindrical Lens Layer
[0119] The thermoplastic resin for cylindrical lens formation has
good transparency, strength, and durability, and, at the same time,
can be extruded and shaped with good stability and operability.
Such thermoplastic resins include polystyrene (PS), polycarbonate
(PC), polymethyl methacrylate (PMMA), polyvinyl chloride (PVC),
polyethylene (PE), tetrafluoroethylene (PTFE), polypropylene (PP),
and copolymer resins containing at least one of these resins.
[0120] The shape of the cylindrical lenses can be properly
determined depending upon a light source. Preferably, the
cylindrical lenses have a lens pitch of not more than 150 .mu.m,
particularly preferably 50 to 100 m, from the viewpoint of moire
caused between the shape and single light source pixels.
[0121] (3) Substrate Film Layer
[0122] The substrate film layer (A2) may be formed of various
thermoplastic resins and thermosetting resins so far as they have
properties required of the substrate for an optical sheet, for
example, transparency, strength, durability and the like. Preferred
thermoplastic resins include polyethylene terephthalate (PET),
polystyrene (PS), polycarbonate (PC), polymethyl methacrylate
(PMMA), polyvinyl chloride (PVC), polyethylene (PE), and
tetrafluoroethylene (PTFE).
[0123] (4) Photosensitive Pressure-sensitive Adhesive Layer
[0124] The photosensitive pressure-sensitive adhesive layer (B)
preferably causes a lowering in adhesive strength of the exposed
part by a radical reaction and is preferably formed of a
photosensitive adhesive which, upon exposure to light, causes, in
its exposed part, a lowering in adhesive strength of not less than
50% as compared with the adhesive strength of the unexposed
part.
[0125] The photosensitive pressure-sensitive adhesive comprises at
least a pressure-sensitive adhesive resin, a photopolymerizable
compound, and a photopolymerization initiator.
[0126] Pressure-sensitive adhesive resins include acrylic resins,
gum resins, silicone resins, urethane resins, and polyester resins.
Among them, acrylic pressure-sensitive adhesives having excellent
durability and adhesion are preferred.
[0127] The acrylic pressure-sensitive adhesive resin is composed
mainly of an acrylic copolymer resin produced by copolymerizing an
alkyl acrylate with other monomer and a functional monomer.
[0128] In the alkyl acrylate, the number of carbon atoms in the
alkyl group is preferably 4 to 15. Examples of such alkyl acrylates
include n-butyl acrylate, 2-ethylhexyl acrylate, isooctyl acrylate,
and isononyl acrylate. They may be used either solely or as a
mixture of two or more.
[0129] Other monomers usable herein include methyl acrylate, methyl
methacrylate, styrene, acrylonitrile, and vinyl acetate. They may
be used either solely or as a mixture of two or more.
[0130] Functional monomers usable herein include, for example,
acrylic acid, methacrylic acid, itaconic acid, hydroxyethyl
acrylate, hydroxyethyl methacrylate, propylene glycol acrylate,
acrylamide, methacrylamide, glycidyl acrylate, glycidyl
methacrylate, dimethylaminoethyl methacrylate, and
tert-butylaminoethyl methacrylate. They may be used either solely
or as a mixture of two or more.
[0131] An acrylic copolymer resin having on its side chain a
photoreactive group, for example, an unsaturated double bond, may
also be used. Specifically, photoreactive group-containing resins
described in Japanese Patent Laid-Open No. 355678/2000 may be
used.
[0132] In the acrylic copolymer resin, the ratio among the alkyl
acrylate, the other monomer(s), and the functional monomer is
preferably 70 to 99 (% by weight) for the alkyl acrylate, 0 to 20
(% by weight) for the other monomer(s), and 0.01 to 20 (% by
weight) for the functional monomer, more preferably 80 to 95 (% by
weight) for the alkyl acrylate, 0 to 10 (% by weight) for the other
monomer(s), and 0.1 to 15 (% by weight) for the functional monomer.
The weight average molecular weight of the acrylic copolymer resin
is 200,000 to 1,200,000, preferably 400,000 to 1,000,000.
[0133] The acrylic pressure-sensitive adhesive may comprise, in
addition to the acrylic copolymer resin, a room temperature
crosslinking-type or heat crosslinking-type crosslinking agent from
the viewpoint of improving cohesive force. Further, a tackifier and
the like may be added to the acrylic pressure-sensitive adhesive
from the viewpoint of modifying the adhesive strength, tackiness,
and viscoelasticity.
[0134] Upon aging of the acrylic pressure-sensitive adhesive under
room temperature conditions, the room temperature crosslinking-type
crosslinking agent causes a crosslinking reaction of the acrylic
pressure-sensitive adhesive. Specific examples of room temperature
crosslinking-type crosslinking agents include polyisocyanate
compounds of polyvalent isocyanates, trimers of these
polyisocyanate compounds, isocyanate-terminated urethane
prepolymers produced by reacting the above polyisocyanate compounds
with polyol compounds, polyisocyanate compounds of these urethane
prepolymers, and trimers of these polyisocyanate compounds.
Specific examples of polyvalent isocyanates include 2,4-tolylene
diisocyanate, 2,5-tolylene diisocyanate, 1,3-xylylene diisocyanate,
1,4-xylylene diisocyanate, diphenylmethane-4,4'-diisocyanat- e,
3-methyidiphenylmethane diisocyanate, hexamethylene diisocyanate,
isophorone diisocyanate, dicyclohexylmethane-4,4'-diisocyanate,
dicyclohexylmethane-2,4'-diisocyanate, and lysine isocyanate.
Chelate compounds of metals such as aluminum and titanium and
polyfunctional epoxy compounds may also be used as the crosslinking
agent.
[0135] The room-temperature crosslinking-type crosslinking agent is
preferably added in an amount of 0.005 to 20 parts by weight,
particularly 0.01 to 10 parts by weight, based on 100 parts by
weight of the acrylic copolymer resin.
[0136] Preferably, the heat crosslinking-type crosslinking agent
causes a crosslinking reaction of the acrylic pressure-sensitive
adhesive upon heating of the acrylic pressure-sensitive adhesive to
100.degree. C. or above, preferably 130.degree. C. or above for 1
to 30 min. Specific examples of such heat crosslinking-type
crosslinking agents include methylol group-containing compounds
produced by reacting formaldehyde with melamine, benzoguamine, urea
or the like, and etherification products of a part or the whole of
the methylol group thereof with aliphatic alcohols. The heating
crosslinking-type crosslinking agent is preferably added in an
amount of 0.01 to 25 parts by weight, particularly preferably 0.1
to 20 parts by weight, based on 100 parts by weight of the acrylic
copolymer resin.
[0137] The tackifier is optionally added for improving the
tackiness of the acrylic pressure-sensitive adhesive. Tackifiers
include rosin resins, terpene resins, and xylene resins. The
tackifier is preferably in an amount of not more than 50% by
weight, particularly preferably not more than 40% by weight, to the
acrylic pressure-sensitive adhesive.
[0138] Photopolymerization compounds may be classified according to
polymerization type, for example, into photoradically polymerizable
compounds, photocationically polymerizable compounds,
photoanionically polymerizable compounds, and compounds which
initiates polymerization through photodimerization. Among them,
photoradically polymerizable compounds are preferred from the
viewpoints of the range of selectable materials, polymerizability
and the like.
[0139] Photoradically polymerizable compounds include compounds
having at least one addition polymerizable ethylenically
unsaturated double bond. Specific examples of photoradically
polymerizable compounds include unsaturated carboxylic acids and
salts thereof, esters of unsaturated carboxylic acids with
aliphatic polyhydric alcohol compounds, and amide bonded products
between unsaturated carboxylic acids and aliphatic polyamine
compounds. More specific examples thereof include monomers of
esters of aliphatic polyhydric alcohol compounds with unsaturated
carboxylic acids. Acrylic esters include, for example, ethylene
glycol diacrylate, triethylene glycol diacrylate, 1,3-butanediol
diacrylate, tetramethylene glycol diacrylate, propylene glycol
diacrylate, neopentyl glycol diacrylate, trimetylolpropane
triacrylate, trimethylolpropane tri(acryloyloxypropyl) ether,
trimethylolethane triacrylate, hexanediol diacrylate,
1,4-cyclohexanediol diacrylate, tetraethylene glycol diacrylate,
pentaerythritol diacrylate, pentaerythritol triacrylate,
pentaerythritol tetraacrylate, dipentaerythritol diacrylate,
dipentaerythritol triacrylate, dipentaerythritol tetraacrylate,
dipentaerythritol hexaacrylate, sorbitol triacrylate, sorbitol
tetraacrylate, sorbitol pentaacrylate, sorbitol hexaacrylate,
tri(acryloyloxyethyl) isocyanurate, polyester acrylate oligomer,
2-phenoxyethyl acrylate, 2-phenoxyethyl acrylate, phenol ethoxylate
monoacrylate, 2-(p-chlorophenoxy)ethyl acrylate, p-chlorophenyl
acrylate, phenyl acrylate, 2-phenylethyl acrylate,
(2-acryloxyethyl) ether of bisphenol A, ethoxylated bisphenol A
diacrylate, 2-(1-naphthyloxy)ethyl acrylate, o-biphenyl acrylate,
o-biphenyl acrylate, 9,9-bis(4-acryloxydiethoxyphenyl)fluorene,
9,9-bis(4-acryloxytriethoxyphe- nyl)fluorene,
9,9-bis(4-acryloxydipropoxyphenyl)fluorene,
9,9-bis(4-acryloxyethoxy-3-methylphenyl)fluorene,
9,9-bis(4-acryloxyethox- y-3-ethylphenyl)fluorene, and
9,9-bis(4-acryloxyethoxy-3,5-dimethyl)fluore- ne.
[0140] Further, sulfur-containing acrylic compounds disclosed in
Japanese Patent Laid-Open No. 72748/1986 may also be used. Examples
thereof include, but are not limited to,
4,4'-bis(.beta.-acryloyloxyethylthio)dip- henylsulfone,
4,4'-bis(.beta.-acryloyloxyethylthio)diphenylketone,
4,4'-bis(.beta.-acryloyloxyethylthio)-3,3',5,5'-tetrabromodiphenylket
one, and 2,4-bis(.beta.-acryloyloxyethylthio)diphenylketone.
[0141] Specific examples of methacrylic esters include such
compounds that, among the above acrylic ester compounds,
"methacrylate" has been substituted for "acrylate", "methacryloxy"
has been substituted for "acryloxy", and "methacryloyl" has been
substituted for "acryloyl".
[0142] These photopolymerizable compounds may be used either solely
or as a mixture of two or more.
[0143] The photopolymerizable compound is preferably added in an
amount of 0.1 to 200 parts by weight, particularly preferably 10 to
150 parts by weight, based on 100 parts by weight of the acrylic
copolymer resin.
[0144] The photopolymerization initiator may be properly selected
according to the polymerization type of the above
photopolymerizable compound. Photopolymerization initiators usable
for photoradically polymerizable compounds include imidazole
derivatives, bisimidazole derivatives, N-arylglycine derivatives,
organic azide compounds, titanocenes, aluminate complexes, organic
peroxides, N-alkoxypyridinium salts, and thioxanthone derivatives.
More specific examples thereof include
1,3-di(t-butyldioxycarbonyl)benzophenone, 3,3',4,4'-tetrakis(t-bu-
tyldioxycarbonyl)benzophenone, 3-phenyl-5-isoxazolone,
2-mercaptobenzimidazole, bis(2,4,5-triphenyl)imidazole,
2,2-dimethoxy-1,2-diphenylethan-1-one (tradename: Irgacure 651,
manufactured by Ciba Specialty Chemicals, K.K.),
1-hydroxy-cyclohexyl-phe- nyl-ketone (tradename: Irgacure 184,
manufactured by Ciba Specialty Chemicals, K.K.),
2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)-butanon- e-1
(tradename: Irgacure 369, manufactured by Ciba Specialty Chemicals,
K.K.), and
bis(.eta.5-2,4-cyclopentadien-1-yl)-bis(2,6-difluoro-3-(1H-pyr-
rol-1-yl)-phenyl)titanium (tradename: Irgacure 784, manufactured by
Ciba Specialty Chemicals, K.K.). Aromatic iodonium salts, aromatic
sulfonium salts, aromatic diazonium salts, aromatic phosphonium
salts, triazine compounds and the like may also be used. Specific
examples thereof include, but are not limited to: iodonium salts,
for example, chlorides, bromides, borofluorides,
hexafluorophosphates, and hexafluoroantimonates of iodonium, such
as diphenyl iodonium, ditolyl iodonium,
bis(p-tert-butylphenyl)iodonium, and bis(p-chlorophenyl)iodonium;
sulfonium salts, for example, chlorides, bromides, borofluorides,
hexafluorophosphates, and hexafluoroantimonates of sulfonium, such
as triphenyl sulfonium, 4-tert-butyltriphenyl sulfonium, and
tris(4-methylphenyl)sulfonium; and 2,4,6-substituted-1,3,5-triazine
compounds, such as 2,4,6-tris(trichloromethyl)-1,3,5-triazine,
2-phenyl-4,6-bis(trichloromethyl)-1,3,5-triazine, and
2-methyl-4,6-bis(trichloromethyl)-1,3,5-triazine compounds.
[0145] These photopolymerization initiators are preferably added in
an amount of 0.5 to 20 parts by weight, particularly preferably 1
to 15 parts by weight, based on 100 parts by weight of the acrylic
copolymer resin.
[0146] A sensitizing dye may be further added from the viewpoint of
improving the sensitivity of the photosensitive pressure-sensitive
adhesive layer for the wavelength of a light source for
sensitization.
[0147] Sensitizing dyes include thiopyrilium salt dyes, merocyanine
dyes, cyanine dyes, quinoline dyes, cumarin dyes, ketocumarin dyes,
xanthone dyes, thioxanthone dyes, rhodamine dyes, cyclopentanone
dyes, and cyclohexanone dyes.
[0148] These sensitizing dyes are preferably added in an amount of
0.01 to 15 parts by weight, particularly preferably 0.1 to 5 parts
by weight, based on 100 parts by weight of the acrylic copolymer
resin.
[0149] Further, various plasticizers, surfactants and the like may
be added from the viewpoints of controlling the adhesive strength
and improving suitability for coating which will be described
later.
[0150] The photosensitive pressure-sensitive adhesive layer is
particularly preferably such that, upon exposure to light, the
adhesive strength of the exposed part is lowered by not less than
50% as compared with the adhesive strength of the unexposed part.
When this photosensitive pressure-sensitive adhesive layer is used,
a good striped light shielding layer which will be described later
can be formed. The adhesive strength is defined as a value
determined by the 180-degree peel strength measurement specified in
JIS Z 0237.
[0151] The photosensitive pressure-sensitive adhesive can be
prepared by dissolving the acrylic copolymer resin, the
photopolymerizable compound, the photopolymerization initiator, and
optional additives such as room temperature crosslinking-type or
heat crosslining-type crosslinking agent, the tackifier, and the
sensitizing dye in a solvent. Solvents usable herein include methyl
ethyl ketone, toluene, ethyl acetate, ethanol, and isopropanol. The
solid content of the photosensitive pressure-sensitive adhesive is
15 to 50% by weight, preferably 20 to 35% by weight.
[0152] Further, a photosensitive pressure-sensitive adhesive layer
may also be formed by coating the solvent-type pressure-sensitive
adhesive directly onto the backside of a cylindrical lens film, or
by the so-called "transfer method" in which the solvent-type
pressure-sensitive adhesive is coated onto a separable substrate
and the coating is then transferred.
[0153] Coating methods usable herein include conventional various
coating methods, for example, die coating, Komma coating, knife
coating, gravure coating, and roll coating. The thickness of the
dried coating is preferably 4 to 30 .mu.m, particularly preferably
5 to 25 .mu.m.
[0154] The photosensitive pressure-sensitive adhesive layer may be
formed by crosslinking treatment, that is, by aging treatment under
room temperature conditions in the case of the room temperature
crosslinking type or by heating to the above-described temperature
in the case of the heat crosslinking type.
[0155] The separable substrate used in the transfer method may be
conventional release paper. Further, a release film prepared by
subjecting the surface of a polyethylene terephthalae film to
release treatment with a fluoro-release agent or a silicone release
agent may also be used. The separable substrate on the side which
is opposite to the pressure-sensitive adhesive layer side may be
subjected to release treatment from the viewpoint of avoiding
blocking caused by protrusion of the pressure-sensitive adhesive
layer formed by coating.
[0156] When the resin composition for photosensitive
pressure-sensitive adhesive layer formation is liquid, the
composition as such may also be coated without the use of any
solvent.
[0157] The coating is exposed to light at a collimation angle of
not more than 10 degrees at least in a direction perpendicular to
the cylindrical lenses. Exposure wavelength and dose may be
determined by taking into consideration, for example, the
composition, mixing amount, and coating thickness of the
photosensitive pressure-sensitive adhesive and the thickness of the
transparent or semitransparent sheet constituting the cylindrical
lenses.
[0158] (5) Striped Light Shielding Part
[0159] The light shielding part (C) is in a stripe form with a
width of not more than 130 .mu.m. The light shielding part is
formed on a focused light-impermeable region by transferring a
light shielding layer transfer sheet, which will be described
later, onto a photosensitive pressure-sensitive adhesive layer.
Since the focused light-impermeable region is in a stripe form, the
light shielding part also becomes a stripe form.
[0160] The pitch of the striped light shielding part is preferably
50 to 90% of the lens pitch. According to the present invention,
since a light shielding part having this narrow pitch can be
provided, a lenticular lens sheet which can provide high-quality
image representation can be realized.
[0161] This light shielding part can easily be formed by utilizing
a light shielding layer transfer sheet which will be described
later.
[0162] (6) Light Shielding Layer Transfer Sheet
[0163] The light shielding layer transfer sheet comprises a light
shielding layer stacked on a transfer sheet substrate. The transfer
sheet substrate may be formed of various materials which have
excellent mechanical strength and have heat resistance, chemical
resistance, solvent resistance, flexibility and the like. Examples
of such materials include: polyester resins such as polyethylene
terephthalate, polybutylene terephthalate, polyethylene
naphthalate, polyethylene terephthalate-isophthalate copolymer, and
terephthalic acid-cyclohexanedimethanol-ethylene glycol copolymer;
cellulosic films; polyamide resins; polyolefin resins; acrylic
resins; vinyl resins; styrene resins; and polycarbonates.
[0164] The transfer sheet substrate may be formed of a copolymer
resin composed mainly of these resins, or a mixture (including an
alloy) of these resins or may be a laminate of a plurality of
layers of them. The transfer sheet substrate may be either a
stretched film or an unstretched film. However, a monoaxially or
biaxially stretched film is suitable from the viewpoint of
improving the strength. If necessary, the resin film may contain a
filler, a plasticizer, an antistatic agent and the like.
[0165] The thickness of the light shielding layer transfer sheet
substrate is generally 5 to 200 .mu.m, particularly preferably 10
to 100 .mu.m. When the thickness is less than 5 .mu.m, the
mechanical strength is unsatisfactory.
[0166] The light shielding layer comprises at least a light
shielding pigment and a binder. The binder preferably has good
transferability, that is, high-resolution transferability, and
thermoplastic resins are preferable. Thermoplastic resins include
vinyl chloride resins, acrylic resins, polyester resins, urethane
resins, amide resins, and cellulosic resins.
[0167] The light shielding pigment is not particularly limited so
far as the pigment has a light shielding property, and carbon black
is preferred.
[0168] The light shielding layer is formed by coating a
low-viscosity composition (ink) prepared by dissolving a binder
such as an acrylic resin, a light shielding pigment and optional
additives such as a dispersant, a plasticizer, and an antistatic
agent in a solvent.
[0169] Coating methods usable herein include conventional printing
or coating methods such as roll coating, reverse roll coating,
gravure coating (gravure printing), gravure reverse coating, Komma
coating, or screen printing.
[0170] Preferably, the above composition possesses high-resolution
transferability and has a ratio between the light shielding pigment
and other dried solid content of at least 1.5.
[0171] (7) Adhesive Layer
[0172] The adhesive layer (D) should be such that this layer can be
formed of any material, can provide satisfactory adhesive strength
of the support (E) to the light shielding part (C) and the
pressure-sensitive adhesive layer (B), and has no substantially
adverse effect on function, properties and the like of the
lenticular lens sheet. The material for constituting the adhesive
layer can be selected by taking into consideration, for example,
materials of the support (E), the light shielding part (C), and the
pressure-sensitive adhesive layer (B) and the adhesive strength.
For example, urethane resins, acrylic resins, and epoxy resins are
usable. The bonding method may be properly selected from a holt
melting method, a heat setting method, an ionizing radiation curing
method, a tackifying method and the like. If necessary, a light
diffusing agent may be added.
[0173] (8) Support
[0174] The support (E) preferably does not substantially have an
adverse effect on function, properties and the like of the
lenticular lens sheet and can retain its shape. Specific examples
of materials for the support (E) include methyl
methacrylate-styrene copolymer resins (MS resins), methacrylic
resins, methyl methacrylate-butadiene-styrene copolymer resins (MBS
resins), polycarbonate, polystyrene, polyvinyl chloride, and
butadiene-styrene copolymer resins.
[0175] If necessary, for example, light diffusing properties,
antireflection properties, antistatic properties, contamination
preventive properties, and scratch resistance properties may be
imparted.
[0176] 5. Production Process of Lenticular Lens Sheet for
Transmission Screen According to Fourth Aspect of Invention
[0177] The production process according to the present invention
comprises the following steps (a) to (f). Each step will be
described.
[0178] (1) Step (a)
[0179] In step (a), a shaping pattern is transferred onto a molten
extruded thermoplastic resin to prepare a not more than 200
.mu.m-thick transparent or semitransparent sheet (A) with
cylindrical lenses being shaped therein at a pitch of not more than
150 .mu.m.
[0180] In the apparatus shown in FIG. B2, for example, the
thermoplastic resin is introduced in a pellet form from a hopper
(15) into a barrel (16) where the thermoplastic resin is heated to
a predetermined temperature. The heated thermoplastic resin is
allowed to flow through a die (17). The flowed thermoplastic resin
(11) is passed through a press contact point (19) between a
pressing roll (18) and a molding roll (12), and is moved according
to the rotation of the molding roll (12). The surface of the
molding roll (12) has a predetermined shaped pattern (12a), and the
thermoplastic resin (11) is shaped by the shaped pattern (12a) into
a cylindrical lens shape. The sheet (13) shaped into the
cylindrical lenses is applied to step (b).
[0181] When a substrate film layer is provided, as shown in FIG.
B5, a substrate film (10) is supplied to the pressing roll
(18).
[0182] (2) Step (b)
[0183] In step (b), a photosensitive pressure-sensitive adhesive
layer (B) is formed on the transparent or semitransparent sheet
(13, A), formed in step (a), on the flat side which is opposite to
the cylindrical lenses.
[0184] FIG. B3 shows an embodiment of the sheet prepared in step
(b). A photosensitive pressure-sensitive adhesive layer (B) is
provided on the transparent or semitransparent sheet (A), composed
of a cylindrical lens layer (A1) and a substrate film layer (A2),
in the flat side which is opposite to the cylindrical lenses.
[0185] Details of the method for the formation of the
photosensitive pressure-sensitive adhesive layer (B) are as
described above.
[0186] (3) Step (c)
[0187] In step (c), light is applied at a collimation angle of not
more than 10 degrees to the sheet, prepared in step (b), on its
side where the cylindrical lenses are formed, whereby the adhesive
strength of the photosensitive pressure-sensitive adhesive in its
part exposed to light focused by the cylindrical lenses is lowered
by a radical reaction.
[0188] The collimation angle is determined by taking into
consideration, for example, a desired width of the light shielding
part and exposure sensitivity of the photosensitive
pressure-sensitive adhesive. Preferably, however, the collimation
angle is not more than 5 degrees. Since the exposed part in the
photosensitive pressure-sensitive adhesive layer (B) is in a stripe
form, the photosensitive pressure-sensitive adhesive layer (B) in
its adhesive strength lowered parts also become the same stripe
form.
[0189] (4) Steps (d) to (f)
[0190] In step (d), a light shielding layer transfer sheet
comprising a material for light shielding part formation is
laminated onto the photosensitive pressure-sensitive adhesive layer
in the sheet prepared in step (c). In step (e), the light shielding
layer transfer sheet laminated in step (d) is separated to transfer
the material for light shielding part formation onto the unexposed
part in the photosensitive pressure-sensitive adhesive layer (B),
thereby forming a striped light shielding part. These steps (d) and
(e) can provide, for example, a sheet as shown in FIG. B4. Details
of the method for the formation of the striped light shielding part
by steps (d) and (e) are as described above.
[0191] In step (f), an adhesive layer (D) and a transparent or
semitransparent support (E) formed of a thermoplastic resin are
formed on the sheet prepared in step (e).
[0192] Step (f) can provide a lenticular lens sheet for a
transmission screen according to the present invention shown, for
example, in FIG. B1.
EXAMPLES
[0193] The following Examples further illustrate the present
invention but do not limit the present invention.
Example A1
[0194] Pellets of a methacryl-butadiene-styrene copolymer resin
(MBS) having a softening temperature of 98.degree. C. were
introduced into a hopper of an extrusion embossing apparatus shown
in FIG. A7.
[0195] This apparatus was provided with a barrel which had been
divided into six parts. The temperatures of the six parts were set
respectively to 165.degree. C., 205.degree. C., 210.degree. C.,
240.degree. C., 250.degree. C., and 250.degree. C. successively in
that order from the part closest to the hopper to the part farthest
from the hopper. The temperature of the die part was set to
250.degree. C. The molten MBS was supplied through this die and
extruded onto a substrate film (a transparent polyester film (PET
film), thickness 50 .mu.m), followed by embossing. At that time,
the molding roll temperature was set to 80.degree. C.
[0196] In this case, the take-off speed of the substrate film was 3
m/min.
[0197] Molding under the above conditions provided an optical sheet
(total thickness 150 .mu.m) according to the present invention
having a cylindrical lens layer with a pitch of 140 .mu.m and a
thickness of 100 .mu.m.
[0198] A photosensitive pressure-sensitive adhesive containing a
radical reaction initiator was coated to a thickness of 20 .mu.m
onto the optical sheet prepared above on the side which is opposite
to the cylindrical lenses. A parallel light radiation was applied
at an exposure corresponding to 200 mJ/cm.sup.2 to the sheet thus
obtained on its cylindrical lens face side. The coating of the
photosensitive pressure-sensitive adhesive only in its sites
through which the radiation focused by the effect of the lenticular
lens shape had been passed as the light path was cured, and the
unexposed parts remained in a tacky state. A black transfer
material was applied to the pressure-sensitive adhesive surface in
this state, and transfer operation was carried out at a transfer
temperature of 60.degree. C. under a pressure of 2 kg/cm.sup.2,
followed by the separation of the transfer material from the
photosensitive tacky surface. Thus, the black transfer material
layer was adhered onto the pressure-sensitive adhesive only in its
unexposed parts to produce a sheet comprising a striped light
shielding layer.
[0199] Further, an acrylic resin adhesive was coated to a thickness
of 50 .mu.m onto the light shielding layer side of this sheet, and
a support (thickness 2 mm) was then stacked on the coating to
produce an optical sheet A1. This support is formed of an MS
material containing 0.08% by weight of a styrene diffusing agent
having an average particle diameter of 10 .mu.m and has a light
diffusing property.
Example A2
[0200] Under the same temperature conditions and take-off speed
conditions as in Example A1, the same resin as used in Example A1
was extruded on the substrate film followed by embossing.
Thereafter, the substrate film was separated to produce a sheet
provided with cylindrical lenses with a pitch of 90 .mu.m and a
thickness of 125 .mu.m.
[0201] Further, in the same manner as in Example A1, a
photosensitive pressure-sensitive adhesive containing a radical
reaction initiator was coated to a thickness of 20 .mu.m. A
parallel light radiation was applied at an exposure corresponding
to 150 mJ/cm.sup.2 to the sheet thus obtained on its cylindrical
lens face side. The coating of the photosensitive
pressure-sensitive adhesive only in its sites through which the
radiation focused by the effect of the lenticular lens shape had
been passed as the light path was cured, and the unexposed parts
remained in a tacky state. A black transfer material was applied to
the pressure-sensitive adhesive surface in this state, and transfer
operation was carried out at a transfer temperature of 60.degree.
C. under a pressure of 2 kg/cm.sup.2, followed by the separation of
the transfer material from the photosensitive tacky surface. Thus,
the black transfer material layer was adhered onto the
pressure-sensitive adhesive only in its unexposed parts to produce
a sheet comprising a striped light shielding layer.
[0202] Further, an acrylic resin adhesive was coated to a thickness
of 50 .mu.m onto the light shielding layer side of this sheet, and
a support (thickness 2 mm) was then stacked on the coating to
produce an optical sheet A2. This support is formed of an MBS
material with a surface subjected to an antiscratch treatment.
Example B1
[0203] MBS pellets having a softening temperature of 98.degree. C.
were introduced into a hopper of an extrusion embossing apparatus
shown in FIG. B2.
[0204] This apparatus was provided with a barrel which had been
divided into six parts. The temperatures of the six parts were set
respectively to 165.degree. C., 205.degree. C., 225.degree. C.,
250.degree. C., 250.degree. C., and 250.degree. C. successively in
that order from the part closest to the hopper to the part farthest
from the hopper. The temperature of the die part was set to
250.degree. C. The molten MBS was extruded through this die into
between a molding roll with cylindrical shapes engraved at a pitch
of 140 .mu.m and a nip roll and was embossed. At that time, the
molding roll temperature was set to 80.degree. C. The take-off
speed was 3 m/min.
[0205] Molding under the above conditions provided a transparent
sheet (total thickness 170 .mu.m) having, on its one side,
cylindrical lenses with a pitch of 140 .mu.m and a thickness of 40
.mu.m.
[0206] An acrylic photosensitive pressure-sensitive adhesive
(tradename: SW-22, manufactured by Soken Chemimal Engineering Co.,
Ltd.) was coated onto the transparent sheet on the side which is
opposite to the cylindrical lenses to a thickness of 20 .mu.m on a
dry basis, and a separate film was applied to the photosensitive
pressure-sensitive adhesive face.
[0207] The peel strength of this photosensitive pressure-sensitive
adhesive was measured by the following method and was found to be
550 gf/inch in an unexposed state and 10 gf/inch after
exposure.
[0208] Measurement of Peel Strength
[0209] 1. A 100 .mu.m-thick polyethylene terephthalate (PET) film
one side of which had been subjected to corona treatment is
provided. A photosensitive pressure-sensitive adhesive is coated
onto the PET film on its corona-treated side to a thickness of 20
.mu.m on a dry basis, and the coating is dried. Thereafter, a PET
film with a surface subjected to release treatment is laminated
onto the dried coating, and the assembly is aged at room
temperature for one week.
[0210] 2. Based on JIS Z 0237, a sample piece (width 1 inch) is
applied to stainless steel (SUS 304), and the assembly is allowed
to stand at room temperature for 24 hr. Thereafter, the peel
strength in an unexposed state and the peel strength after exposure
at 200 mJ/cm.sup.2 are measured.
[0211] Ultraviolet light with wavelengths including a wavelength of
365 nm was applied at 150 mJ/cm.sup.2 and a collimation angle of 5
degrees from the cylindrical lens face side of the sheet thus
obtained. The coating of the photosensitive pressure-sensitive
adhesive only in its sites through which the ultraviolet light
focused by the effect of the cylindrical lens shape had been passed
as the light path caused a lowering-in adhesive strength, and the
unexposed parts remained in a tacky state.
[0212] The separate film was separated, and a light shielding sheet
was then applied to the surface of the pressure-sensitive adhesive.
Lamination was carried out under conditions of temperature
80.degree. C. and pressure 5 kg/cm.sup.2. Thereafter, the light
shielding sheet was separated from the surface of the
photosensitive pressure-sensitive adhesive.
[0213] The light shielding sheet was prepared as follows. A 25
.mu.m-thick PET film was provided as a light shielding layer
transfer sheet substrate. The following composition (ink) for a
light shielding layer was coated onto the substrate by gravure
reverse coating at a coverage of 1.0 g/m.sup.2 on a dry basis, and
the coating was dried to form a light shielding layer. Thus, a
light shielding sheet was prepared.
[0214] The composition (ink) for a light shielding layer was
prepared by dispersing and dissolving 10 parts by mass of an
acrylic resin, 20 parts by mass of carbon, and 2 parts by mass of a
dispersant in 68 parts by mass of a mixed solvent composed of equal
amounts of toluene and methyl ethyl ketone.
[0215] Thus, the black ink was adhered only onto the unexposed part
of the pressure-sensitive adhesive to form a striped light
shielding layer.
[0216] Further, an acrylic adhesive was coated to a thickness of 50
.mu.m onto the light shielding layer side of the optical sheet.
Subsequently, a support (thickness 2 mm) was stacked on the coating
to produce a lenticular lens sheet B1 for a transmission screen.
This support is formed of an MS material containing 0.08% by weight
of a styrene diffusing agent having an average particle diameter of
10 .mu.m and has a light diffusing property.
Example B2
[0217] In the same material, extruder, and temperature conditions
as in Example B1, extrusion and embossing were carried out between
a molding roll with cylindrical shapes engraved at a pitch of 90
.mu.m and a nip roll. At that time, the take-off speed was 5 m/min.
In this case, any substrate film was not used.
[0218] Molding under the above conditions provided a 130
.mu.m-thick transparent sheet having, on its one side, cylindrical
lenses with a pitch of 90 .mu.m and a height of 25 .mu.m.
[0219] A photosensitive pressure-sensitive adhesive was coated by
die coating onto a separate film to a thickness of 20 .mu.m, and
this sheet was applied to the transparent sheet on the side which
is opposite to the cylindrical lenses. The photosensitive
pressure-sensitive adhesive was the same as that used in Example
B1.
[0220] Ultraviolet light with wavelengths including a wavelength of
365 nm was applied at 100 mJ/cm.sup.2 and a collimation angle of 5
degrees from the cylindrical lens face side of the sheet thus
obtained. The coating of the photosensitive pressure-sensitive
adhesive only in its sites through which the ultraviolet light
focused by the effect of the cylindrical lens shape had been passed
as the light path caused a lowering in adhesive strength, and the
unexposed parts remained in a tacky state.
[0221] The separate film was separated, and a light shielding sheet
was then applied to the surface of the pressure-sensitive adhesive.
Lamination was carried out under conditions of temperature
80.degree. C. and pressure 5 kg/cm.sup.2. Thereafter, the light
shielding sheet was separated from the surface of the
photosensitive pressure-sensitive adhesive. The light shielding
sheet was the same as that used in Example B1.
[0222] Thus, the black ink was adhered only onto the unexposed part
of the pressure-sensitive adhesive to form a striped light
shielding layer.
[0223] Further, an acrylic adhesive was coated to a thickness of 50
.mu.m onto the light shielding layer side of the optical sheet.
Subsequently,
[0224] a support (thickness 2 mm) was stacked on the coating to
produce a lenticular lens sheet B2 for a transmission screen. This
support is formed of an MS material having a surface subjected to
antiscratch treatment and antireflection treatment.
* * * * *